To improve network traffic, hierarchical radio access networks often include both macrocells and small cells that service areas that service portions of the macrocells. The small cells can extend the reach of the hierarchical radio access network. The small cells are frequently positioned in areas where signal strength of a macrocell is poor or where data traffic demand is high. The small cells may provide UEs with higher quality radio network access compared with the macrocell.
A hierarchical radio access network may include many small cells that each services a limited geographical area. These small cells are positioned within the coverage area of a macrocell. A network operator can flexibly install small cells in places that require higher data traffic capacity.
When a UE moves into the coverage area of a small cell, the UE performs a handover operation from the macrocell (or another small cell) and thus offloads some traffic from the macrocell to the small cell. Thus, the number of supported, active UEs in the coverage increases and the overall data traffic capacity for the area is also increased.
Offloading some traffic to a small cell provides a benefit to the operator, but these processes are not without drawbacks. A small cell typically includes a small cellular base station that covers only a small geographical area, as mentioned above. For example, a typical small cell range may be 200 meters wide or less compared with a typical macrocell having a typical range (broadcast area) that is a of couple of kilometers wide.
A small cell may operate identically to the macrocell with the exception that the coverage area of the small cell is smaller than that of the macrocell, so the transmission power of the small cell is also lower compared to the macrocell. A UE close to the coverage area of a small cell may detect that a channel quality of the small cell is better than the macrocell. Based on the existing handover mechanism, the UE reports a signal strength measurement report to the network, and the network determines whether the small cell is a better candidate for the UE than the macrocell. If so, the network then performs a handover of the UE to the small cell.